Diffusion of volatile organics through contact lenses

The purpose of this study was to determine the effect of contact lenses on the exposure of eyes to vapors of organic solvents. Vials of normal saline with and without contact lens barriers were exposed to known concentrations of vapors of acetone, diethyl ether, trichloroethylene (TCE), and toluene. Uptake in vials with hydrogel polymacon (38% water content) lens interfaces was consistently lower than in control vials for exposure times of 2 minutes to 4 hours. Average concentrations were 54%, 26%, 28%, and 25% of the control for acetone, ethyl ether, TCE, and toluene, respectively. After removal from the test chambers, vials with polymacon lenses in place retained ethyl ether, TCE, and toluene significantly longer than control vials without lenses, and concentrations were generally equal in experimental and control vials 24 hours after removal. Uptake across rigid gas permeable lenses (RGP) (silicone/acrylate and fluoropolymer) and hydrogel lenses (polymacon, vifilcon A and etafilcon A) was positively correlated with the water content of the lenses. Uptake across hydrogel lenses ranged from approximately 10 to over 100 times the uptake across RGP lenses for all test compounds except acetone after exposure times of 4 minutes and 30 minutes. Based on these data, we conclude that contact lenses worn in environments containing volatile organic solvents may decrease the exposure of the eye to these compounds.